In a nutshell, these two units each contain a Double Oven Controlled Quartz Crystal Oscillator (DOCXO) made by Milliren (MTI). Both of these oscillators are GPS disciplined using an onboard GPS timing receiver located in the REF 1 box.

These are NOS (new old stock) surplus units which were manufactured around 2000. The useful outputs are 10 and 15Mhz and 1PPS. It will be very interesting to see how this unit performs over the long term.